'parameter' : no directional parameter attribute specified, defaulting to [in]
A method on a parameter in an attributed interface does not have one of the directional attributes: in or out. The parameter defaults to in.
The following sample generates C4682:
#include <windows.h> [module(name="MyModule")]; [ library_block, object, uuid("c54ad59d-d516-41dd-9acd-afda17565c2b") ] __interface IMyIface : IUnknown { HRESULT f1(int i, int *pi); // try the following line // HRESULT f1([in] int i, [in] int *pi); }; void main() { }